Dokonalé není...

Hello,
I brought a coaster from Prague with an inscription that says: Dokonalé není třeba měnit and although all the words are in the dictionary, the meaning of the phrase escapes... Can someone help, please?
Thanks

................Dokonalénení třebaměnit
Literally: The perfect it is not necessaryto change, so: if it's perfect (already), there's no need to change it.
More idiomatically: If it ain't broke, don't fix it!

It's one of the advertising slogans adopted by a very well-known brand of Czech beer. In this particular context, I think it's appealing to the consumer's sense of the beer's tradition and quality. They've been brewing it this way for hundreds of years, everyone knows it's excellent beer, so why even think about changing the recipe or production technique? There's no need to. Stick with what you already know is good. Don't tinker with it.